No one likes it

Turbulence is defined as an irregular motion of air resulting from eddies or rising currents. It can cause erratic movements of pitch, roll, and yaw. We’ve seen the stories on the news about passengers injured in turbulence or even damage to airframes, but still those instances are rare. No one likes turbulence. It is annoying and sometimes sickening for passengers. What can you do as a pilot to minimize the bumps?

First, we must look at what creates the bumps. Turbulence is created by a variety of factors including terrain, wind shear, thunderstorms, and thermals. Some is easily avoided, and some isn’t.

Thermal turbulence

Most of us have determined that turbulence in the lower altitudes where most piston aircraft fly can be avoided by flying early in the day or during the evening. The peak time for a rough ride from thermally induced turbulence is between 1 p.m. to 5 p.m. Why? Favorable conditions for low-level thermal turbulence include warm surface temperatures and uneven surface heating. The differential heating of the Earth’s surface creates thermals or rising parcels of air. Paved areas reflect more radiation and vegetation absorbs more radiation. When I was learning to fly gliders, we would seek out areas that reflected radiation to stay airborne longer. You can often climb above a broken or scattered cloud layer and avoid most thermal turbulence.

Mountain turbulence

Mountains create turbulence through mechanical means. The terrain acts as a barrier to the prevailing wind flow. When the winds strike the mountains, the air is forced upward and can encounter a stable layer and be redirected toward the surface. Winds greater than 25 knots blowing perpendicular to the top of the mountain ridge are favorable for mountain waves to develop. Lenticular clouds are a visual clue for pilots that mountain waves exist. Rotor clouds are often associated with the most intense turbulence. These rotors can result in vertical currents at 2,000 feet a minute. Extreme turbulence near mountains can be especially dangerous for pilots inexperienced in mountain flying.

Frontal turbulence

Fractus clouds that look like cloud fragments are found under the cloud base. They are sheared by strong winds, giving them a ragged appearance on the bottom of the clouds. These clouds are a visual sign of a rough ride.

Wind shear-related turbulence

This type of turbulence is most common in the flight levels where turbine-powered aircraft spend most of their time. Wind shear is defined as a change in wind speed or direction over a short distance and can occur either horizontally or vertically. You will often notice the ride will get bumpy when winds shift direction quickly. Another visual cue to velocity related wind shear between two layers is Kelvin-Helmholtz waves. These waves are characterized by their appearance similar to ocean waves.

For those with glass panels in the cockpit, you may have noticed this with the wind indicator on the primary flight display. A common example of this change is transitioning from a headwind to a tailwind. Wind-shear-related turbulence often occurs near the jetstream and around temperature inversions. This is an area where the temperature increases with altitude.

Clear air turbulence (CAT)

This turbulence is typically found at altitudes above 15,000 feet. CAT occurs most frequently during the winter months when the jetstream is much stronger. This type of turbulence can be among the most challenging to avoid. Understanding that the depth of the turbulence is usually around 2,000 feet gives the pilot some insight on altitude changes, which can help improve the ride conditions.

Thunderstorm-related turbulence

The updrafts and downdrafts associated with thunderstorms can result in loss of aircraft control to structural damage. This is why thunderstorms must be avoided at all costs. Do not fly under thunderstorms even if the visibility is good. The extreme nature of the convection within a thunderstorm can send an aircraft on a wild ride at 6,000 feet per minute. The worst of thunderstorm-related turbulence usually happens between 10,000 and 20,000 feet. As expected, the worst storms are those with the most vertical development. Thunderstorms have been known to produce extreme turbulence as far as 20 nautical miles from the parent storm. Request a wide deviation from air traffic control to give yourself and your passengers some added protection. A good rule of thumb is to avoid flying through any build-ups with a cloud depth higher than 10,000 feet.

Thunderstorms have been known to produce extreme turbulence as far as 20 nautical miles from the parent storm. Request a wide deviation from air traffic control to give yourself and your passengers some added protection.A variety of resources are available for flight planning to help you avoid the bumps. The turbulence imagery available on your favorite electronic flight bags originate from NOAA’s Aviation Weather Center in Kansas City. Those graphical products center around something called the Eddy Dissipation Rate (EDR). This rate is derived from model data and essentially shows how much the air is mixing. The more mixing in the atmosphere the bumpier the ride. On the aviationweather.gov website, the turbulence product is user configurable with a sliding altitude scale as well as a forecast time extending to 18 hours.

Keep in mind that what is severe turbulence for one aircraft may not be the same for another. Light to moderate turbulence for a Boeing 767 could be severe turbulence for a Piper Cherokee. Fortunately, the legend for these products reflects light, medium, and heavy categories of aircraft. It is also important to note with pilot reports, or pireps, what type aircraft reported the turbulence.

While turbulence will always be part of aviation, there are ways we pilots can minimize the worst of it through improved flight planning and watching for visual cues once in the air. In the meantime, I will keep analyzing the data to give my wife a more comfortable flight.

JP Dice is a veteran meteorologist, flight instructor, and corporate pilot flying Cessna Citations and Gulfstreams.